World Housing Encyclopedia an Encyclopedia of Housing Construction in

Seismically Active Areas of the World

an initiative of Earthquake Engineering Research Institute (EERI) and

International Association for Earthquake Engineering (IAEE)

HOUSING REPORT Unreinforced brick masonry building with

reinforced concrete roof slab

Report # 21

Report Date 06-05-2002

Country INDIA

Housing Type Unreinforced Masonry Building

Housing Sub-Type Unreinforced Masonry Building : Brick masonry in lime/cement mortar

Author(s) Ravi Sinha, Svetlana N. Brzev

Reviewer(s) Svetlana N. Brzev

Important This encyclopedia contains information contributed by various earthquake engineering professionalsaround the world. All opinions, findings, conclusions & recommendations expressed herein are those of thevarious participants, and do not necessarily reflect the views of the Earthquake Engineering ResearchInstitute, the International Association for Earthquake Engineering, the Engineering InformationFoundation, John A. Martin & Associates, Inc. or the participants' organizations.

Summary

Typical rural and urban construction in western and southern India. This construction iswidely prevalent among the middle-class population in urban areas and has become popular inrural areas in the last 30 years. Brick masonry walls in cement mortar function as the main

load-bearing element. The roof structure is a cast-in-situ reinforced concrete slab. Ifconstructed without seismic features, buildings of this type are vulnerable to earthquakeeffects. They exhibited rather poor performance during the Koyna (1967), Killari (1993),Jabalpur (1997), and Bhuj (2001) earthquakes in India.

1. General InformationBuildings of this construction type can be found in all parts of southern and western India. About 20% of housingunits in Maharashtra state (approximately 3 million housing units in total) are of this type. Their number in urbanareas is greater, and about 30% of all houses in Mumbai are of this type. Similar construction technology is used innorthern and eastern India, but the bricks in those areas are of far superior quality. This type of housing constructionis commonly found in both rural and urban areas.

Most buildings in rural areas are of single-storey construction, however in urban areas multi-family housing of thistype is very common.

This construction type has been in practice for less than 75 years.

Currently, this type of construction is being built. Cement mortar and reinforced concrete are relatively recentintroduction to the local construction practice. These houses may be up to 50-60 years old in urban areas while thepenetration of cement in rural constructions is more recent. This is the construction practice of choice amongst thelower middle class and middle class in both rural and urban areas. In rural areas, even the rich generally prefer brickmasonry structures with RCC roof slabs.

Figure 1: Typical Building

Figure 1A: Typical Rural Building

Figure 2A: Key Load-Bearing Elements - ABuilding Under Construction

Figure 2B: Key Load-Bearing Elements - ABuilding Under Construction

2. Architectura l Aspects

2.1 Siting These buildings are typically found in flat, sloped and hilly terrain. They do not share common walls with adjacent

buildings. This housing type is found on both flat and hilly terrain. However, brick masonry houses are not

constructed on a very steep terrain When separated from adjacent buildings, the typical distance from a neighboring

building is 3-5 meters.

2.2 Building Configuration The building type is typically regular, mainly rectangular in plan. However, some buildings on sloping terrain may havesplit-level leading to stiffness discontinuity. The houses typically have one door opening and one or two windowopenings per wall. The openings are typically away from the edges (>0.75 m). The windows are typically 1.25 m² andthe doors are typically 1.75 m² The total opening length is typically 20-25% of wall length. RCC lintel beams arecommonly provided over the openings.

2.3 Functional Planning The main function of this building typology is single-family house. Single houses of this type are in rural areas. A lotof multiple housing units are found in urban areas. A small number of houses are of a mixed use (commercial onground floor, and residential on other floors). The economic significance of damage to such mixed units for the localcommunity may be significant and disproportionate to the number of such buildings. In a typical building of this

type, there are no elevators and 1-2 fire-protected exit staircases. Usually there is not additional door besides the main

entry in this building type.

2.4 Modification to Building In urban areas, additional floors are often added without considering structural aspects. The construction is thereforestaggered and a gap of several years may exist between the construction of different portions of the building. In ruralareas, where population density is lower, horizontal building expansion is more common.

Figure 3: Plan of aTypical Building

3. Structura l Deta ils

3.1 Structura l System Materia l Type of Load-Bearing Structure # Subtypes Most appropriate type

Stone Masonry Walls

1Rubble stone (field stone) in mud/lime mortar or w ithout mortar (usually w ith timber roof)

☐

2 Dressed stone masonry (inlime/cement mortar) ☐

Adobe/ Earthen Walls

3 Mud w alls ☐4 Mud w alls w ith horizontal w ood elements ☐5 Adobe block w alls ☐

Masonry

6 Rammed earth/Pise construction ☐

Unreinforced masonryw alls

7 Brick masonry in mud/limemortar ☐

8 Brick masonry in mud/limemortar w ith vertical posts ☐

9 Brick masonry in lime/cementmortar ☑

10 Concrete block masonry incement mortar ☐

Confined masonry

11 Clay brick/tile masonry, w ithw ooden posts and beams ☐

12Clay brick masonry, w ithconcrete posts/tie columnsand beams

☐

13 Concrete blocks, tie columnsand beams ☐

Reinforced masonry

14 Stone masonry in cementmortar ☐

15 Clay brick masonry in cementmortar ☐

16 Concrete block masonry incement mortar ☐

Structural concrete

Moment resistingframe

17 Flat slab structure ☐18 Designed for gravity loads

only, w ith URM infill w alls ☐

19 Designed for seismic effects,w ith URM infill w alls ☐

20 Designed for seismic effects,w ith structural infill w alls ☐

21 Dual system – Frame w ithshear w all ☐

Structural w all22 Moment frame w ith in-situ

shear w alls ☐

23 Moment frame w ith precastshear w alls ☐

Precast concrete

24 Moment frame ☐25 Prestressed moment frame

w ith shear w alls ☐26 Large panel precast w alls ☐27 Shear w all structure w ith

w alls cast-in-situ ☐

28 Shear w all structure w ithprecast w all panel structure ☐

Steel

Moment-resistingframe

29 With brick masonry partitions ☐30 With cast in-situ concrete

w alls ☐31 With lightw eight partitions ☐

Braced frame32 Concentric connections in all

panels ☐

33 Eccentric connections in afew panels ☐

Structural w all34 Bolted plate ☐35 Welded plate ☐

Timber Load-bearing timberframe

36 Thatch ☐37 Walls w ith bamboo/reed mesh

and post (Wattle and Daub) ☐

38Masonry w ith horizontalbeams/planks at intermediatelevels

☐

39 Post and beam frame (nospecial connections) ☐

40Wood frame (w ith specialconnections) ☐

41

Stud-w all frame w ithplyw ood/gypsum boardsheathing

☐

42 Wooden panel w alls ☐

OtherSeismic protection systems

43 Building protected w ith base-isolation systems ☐44 Building protected w ith

seismic dampers ☐Hybrid systems 45 other (described below ) ☐

3.2 Gravity Load-Resisting System The vertical load-resisting system is un-reinforced masonry walls. The gravity load is carried by the masonry walls.The roof slab rests directly on the walls, and the total load is transferred to the foundation. The foundation generallyconsists of brick masonry or stone masonry strip footing. In rural areas, the walls are directly extended into theground; the behavior of these foundations is similar to strip footing.

3.3 Latera l Load-Resisting System The lateral load-resisting system is un-reinforced masonry walls. The lateral load is carried by the walls in the directionof seismic forces. The masonry walls thus act as shear walls. The RCC roofs are generally flat and are directly supportedon the walls, and act as rigid diaphragm. The lateral loads in these structures are distributed to the walls through theRCC slab. In rare situations where the RCC slabs are not horizontal or where the slabs do not act rigidly, the lateralloads are not fully distributed to the different shear walls.

3.4 Building Dimensions The typical plan dimensions of these buildings are: lengths between 10 and 20 meters, and widths between 5 and 20meters. The building has 1 to 4 storey(s). The typical span of the roofing/flooring system is 6 meters. TypicalStory Height: Approximately 3 m per floor. Typical Span: The wall spans between two adjacent parallel walls typicallyrange from 5 to 8 m. The typical storey height in such buildings is 3 meters. The typical structural wall density is up

to 20 %. The wall density typically ranges from 0.12 to 0.15.

3.5 Floor and Roof System

Materia l Description of floor/roof system Most appropriate floor Most appropriate roof

MasonryVaulted ☐ ☐Composite system of concrete joists andmasonry panels ☐ ☐

Structural concrete

Solid slabs (cast-in-place) ☑ ☑Waffle slabs (cast-in-place) ☐ ☐Flat slabs (cast-in-place) ☐ ☐Precast joist system ☐ ☐Hollow core slab (precast) ☐ ☐Solid slabs (precast) ☑ ☑Beams and planks (precast) w ith concretetopping (cast-in-situ) ☐ ☐Slabs (post-tensioned) ☐ ☐

Steel Composite steel deck w ith concrete slab(cast-in-situ) ☐ ☐Rammed earth w ith ballast and concrete orplaster finishing ☐ ☐Wood planks or beams w ith ballast and concrete or plaster finishing ☐ ☐

Timber

Thatched roof supported on w ood purlins ☐ ☐Wood shingle roof ☐ ☐Wood planks or beams that support clay tiles ☐ ☐Wood planks or beams supporting naturalstones slates ☐ ☐Wood planks or beams that support slate,metal, asbestos-cement or plastic corrugatedsheets or tiles

☐ ☐

Wood plank, plyw ood or manufactured w oodpanels on joists supported by beams or w alls ☐ ☐

Other Described below ☑ ☑

The RCC roof slabs typically act as rigid diaphragm. On the ground floor, RCC slabs are not provided. In multi-storeyconstructions all other floors have RCC floor slabs.

3.6 Foundation

Type Description Most appropriate type

Shallow foundation

Wall or column embedded insoil, w ithout footing ☑Rubble stone, fieldstoneisolated footing ☐Rubble stone, fieldstone stripfooting ☑Reinforced-concrete isolatedfooting ☐Reinforced-concrete stripfooting ☐Mat foundation ☐No foundation ☐

Deep foundation

Reinforced-concrete bearingpiles ☐Reinforced-concrete skinfriction piles ☐Steel bearing piles ☐Steel skin friction piles ☐Wood piles ☐Cast-in-place concrete piers ☐Caissons ☐

Other Described below ☐

Figure 4A: Critical Structural Details - Full BrickWall Section

Figure 4B: Critical Structural Details - Half BrickWall Details

Figure 4C: Key Structural Details: Wall-slabConnection (slab may also extend for a full w all

thickness)

Figure 5A: Key Seismic Resilient Features - RCLintel Band and Good Quality Construction; noteexample of a building that sustained the effects of

the 1993 Killari earthquake (M6.4) w ithout damagealthough located very close to the epicentre

Figure 5B: Construction Deficiency - ExcessivelyThick Mortar Bedding Joints Figure 5C: Construction Deficiency -

Discontinuous RC Lintel Band (Bond Beam)

Figure 5D: Construction Deficiency -Discontinuous RC Lintel Band

Figure 5E: Construction Deficiency - ExposedSteel Reinforcement in RC Lintel Band

Construction

4. Socio-Economic Aspects

4.1 Number of H ousing Units and Inhabitants Each building typically has 1 housing unit(s). 1 units in each building. Typically one housing unit per building (ruralareas) and a good mix of single and multi-family dwellings (urban areas). The number of inhabitants in a buildingduring the day or business hours is 5-10. The number of inhabitants during the evening and night is 11-20.

4.2 Patterns of Occupancy In rural areas, houses of this type are typically occupied by a single extended family, with several generations stayingtogether. In urban areas, the houses may be multiple housing units with different families living in differentapartments/floors.

4.3 Economic Level of Inhabitants

Income class Most appropriate type

a) very low -income class (very poor) ☐b) low -income class (poor) ☐c) middle-income class ☑d) high-income class (rich) ☑

Brick masonry houses are used by lower middle class and middle class in both rural and urban areas, and the rich classin rural areas. The middle class dwellings are typically smaller in size (less than 100 m²) while the rich class dwellingsmay be much larger and even multi-storied.

Ratio of housing unit price to annual income Most appropriate type

5:1 or w orse ☐4:1 ☐3:1 ☐

1:1 or better ☑

What is a typica l source offinancing for bu ildings of thistype?

Most appropriate type

Ow ner financed ☐Personal savings ☑Informal netw ork: friends andrelatives ☑Small lending institutions / micro-finance institutions ☐Commercial banks/mortgages ☐Employers ☐Investment pools ☐Government-ow ned housing ☐Combination (explain below ) ☐other (explain below ) ☐

In each housing unit, there are no bathroom(s) without toilet(s), no toilet(s) only and no bathroom(s) includingtoilet(s).

In rural areas, bathrooms and toilets are usually constructed separately from the houses. In urban areas, it is commonto find at least two toilets in each dwelling or housing unit. .

4.4 Ownership The type of ownership or occupancy is renting and outright ownership.

Type of ownership oroccupancy? Most appropriate type

Renting ☑outright ow nership ☑Ow nership w ith debt (mortgageor other) ☐Individual ow nership ☐Ow nership by a group or pool ofpersons ☐Long-term lease ☐other (explain below ) ☐

5. Seismic Vulnerability

5.1 Structura l and Architectura l Features Structura l/Architectura lFeature

StatementMost appropriate type

Yes No N/A

Lateral load path

The structure contains a complete load path for seismicforce effects from any horizontal direction that servesto transfer inertial forces from the building to thefoundation.

☐ ☑ ☐

Building The building is regular w ith regards to both the plan

Configuration and the elevation. ☑ ☐ ☐

Roof construction

The roof diaphragm is considered to be rigid and it isexpected that the roof structure w ill maintain itsintegrity, i.e. shape and form, during an earthquake ofintensity expected in this area.

☐ ☑ ☐

Floor construction

The floor diaphragm(s) are considered to be rigid and itis expected that the floor structure(s) w ill maintain itsintegrity during an earthquake of intensity expected inthis area.

☐ ☑ ☐

Foundationperformance

There is no evidence of excessive foundation movement(e.g. settlement) that w ould affect the integrity orperformance of the structure in an earthquake.

☐ ☐ ☑

Wall and framestructures-redundancy

The number of lines of w alls or frames in each principaldirection is greater than or equal to 2. ☑ ☐ ☐

Wall proportions

Height-to-thickness ratio of the shear w alls at each floor level is:

Less than 25 (concrete w alls);

Less than 30 (reinforced masonry w alls);

Less than 13 (unreinforced masonry w alls);

☐ ☑ ☐

Foundation-w allconnection

Vertical load-bearing elements (columns, w alls)are attached to the foundations; concretecolumns and w alls are dow eled into thefoundation.

☐ ☑ ☐

Wall-roofconnections

Exterior w alls are anchored for out-of-plane seismiceffects at each diaphragm level w ith metal anchors orstraps

☐ ☑ ☐

Wall openings

The total w idth of door and w indow openings in a w allis:

For brick masonry construction in cement mortar : lessthan ½ of the distance betw een the adjacent crossw alls;

For adobe masonry, stone masonry and brick masonryin mud mortar: less than 1/3 of the distance betw eenthe adjacent crossw alls;

For precast concrete w all structures: less than 3/4 ofthe length of a perimeter w all.

☐ ☑ ☐

Quality of building materialsQuality of building materials is considered to beadequate per the requirements of national codes andstandards (an estimate).

☐ ☑ ☐

Quality of w orkmanshipQuality of w orkmanship (based on visual inspection offew typical buildings) is considered to be good (perlocal construction standards).

☐ ☑ ☐

MaintenanceBuildings of this type are generally w ell maintained and thereare no visible signs of deterioration of buildingelements (concrete, steel, timber)

☐ ☑ ☐

Additional Comments

5.2 Seismic Features Structura lElement Seismic Deficiency Earthquake Resilient Features Earthquake Damage Patterns

Wall - Absence of RC bands or poorly constructed bands - Brickmasonry strength very low - Poor mortar quality; excessivelythick bedding joints - load-bearing w alls not properly interlocked- Poor quality of construction - Openings are not properlyproportioned; the distance betw een corner and opening is not

as per recommended practice

- When present, seismic features (inparticular RC bands) are very effectivein enhancing seismic resistance, asconfirmed in the 1993 Killariearthquake (Figure 5A) and 2001Bhuj earthquake (Figure 6j)

- Shear cracks in the w alls, mainlystarting from corners of openings. -Partial or complete out-of-planew all collapse due to the lack ofw all-roof anchorage and large w all

slenderness ratio

Frame(columns,beams)

Roof andfloors

- Roof not integrally connected to w alls (poor torsionalresistance) - Poor quality concrete may compromise rigid

diaphragm action - Poor maintenance

- Partial caving-in of roof due tocollapse of supporting w alls -Horizontal crack at the w all-roofconnection - Shifting of roof fromthe w all due to torsional motion of

roof slab. Other

5.3 Overall Seismic Vulnerability Rating The overall rating of the seismic vulnerability of the housing type is B: MEDIUM-HIGH VULNERABILITY (i.e., poorseismic performance), the lower bound (i.e., the worst possible) is A: HIGH VULNERABILITY (i.e., very poor seismic

performance), and the upper bound (i.e., the best possible) is C: MEDIUM VULNERABILITY (i.e., moderate seismic

performance).

Vulnerability high medium-high medium medium-low low very low

very poor poor moderate good very good excellent

VulnerabilityClass

A B C D E F

☑ ☐ ☑ ☐ ☐ ☐

5.4 H istory of Past Earthquakes Date Epicenter, region Magnitude Max. Intensity

1967 Koyna 6.7 VIII (MSK) 1993 Killari 6.4 VIII (MSK) 1997 Jabalpur 6.1 VII (MSK) 2001 Bhuj 7.6 X (MSK)

Building construction of this type (without seismic provisions) suffered significant damage during Koyna (1967) andKillari (1993) earthquakes. Some damage was also observed during Jabalpur (1997) earthquake. The main damagepatterns consisted of: shear cracks in walls, mainly starting from corners of openings; partial out of plane collapse ofwalls; partial caving-in of roofs due to collapse of supporting walls, and shifting of roof from wall due to torsionalmotion of roof slab. This construction has experienced moderate to very heavy damage in the 2001 Bhuj earthquake(M 7.6). In the epicental region several buildings of this type suffered total collapse of the walls resulting in the deathand injury to a large number of people. The overall building performance was dependent on the type of roof system:buildings with lightweight roof suffered relatively less damage while buildings with RC roofs suffered much greaterdamage (Source: IIT Powai 2001). Importance and effectiveness of seismic provisions was confirmed both in the 1993Killari earthquake and the 2001 Bhuj earthquake. A building with RC lintel band (located in the Killari village only fewkilometers away from the epicentre) shown on Figure 5a sustained the earthquake effects with a minor damage whilelarge majority of other buildings in the same village collapsed, causing over 1,400 deaths. Similarly, unreinforcedmasonry buildings with RC bands sustained the effects of the 2001 Bhuj earthquake with moderate damage while theneighbouring buildings of similar construction without seismic provisions collapsed (see Figure 6J).

Figure 6A: Typical Earthquake Damage - RoofCollapse Caused by the Wall Collapse (1993 Killari

Earthquake)

Figure 6B: Typical Earthquake Damage - WallCorner Cracking (1993 Killari Earthquake)

Figure 6C: Typical Earthquake Damage - WallCracking above the Door Opening (1993 Killari

Earthquake)

Figure 6D: Typical Earthquake Damage - WallCorner Failure (1993 Killari Earthquake)

Figure 6E: Typical Earthquake Damage - SlidingFailure of Roof-Wall Connection Due to theAbsence of Wall Reinforcement (1993 Killari

Earthquake)Figure 6F: Typical Earthquake Damage: In-Plane

Wall Cracking (1993 Killari Earthquake)

Figure 6G: Partial Building Collapse in the 1997Jabalpur Earthquake

Figure 6H: Faillure of Brick Masonry Walls in the1997 Jabalpur Earthquake

Figure 6I: Collapse of Brick Masonry Buildings inthe 2001 Bhuj Earthquake (Source: IIT Pow ai,

2001)

Figure 6J: View of a Collapsed traditional brickmasonry building in cement mortar (foreground)and masonry building w ith lintel bands w hichsustained only a moderate damage in the 2001

Bhuj earthquake (Source: IIT Pow ai, 2001)

6. Construction

6.1 Building Materia ls

Structura lelement

Bu ildingmateria l Characteristic strength Mix proportions/dimensions Comments

WallsBrickCementmortar.

< 2.5 MPa (compressive)Low compressive strength(< 5 MPa).

Typical brick size 230 mm X 115 mm X 75mm 1:6 cement/sand mortar.

Bricks are low strength Very low compressiveand shear strength.

Foundation

Stone orbrickCementmortar.

Brick: < 2.5 MPa (lowcompressive strength) Lowcompressive strength (< 5MPa).

Typical brick size 230 mm X 115 mm X 75mm or locally available uncoursed randomrubble stone blocks are used 1:6 cement/sandmortar.

Bricks are low strength. Stone blocks are highstrength but are uncoursed and have poorbond. Very low compressive and shearstrength.

Frames(beams &columns)

Roof andfloor(s)

Reinforcedconcrete.

Compressive strength (10-20MPa).

1:2:4 to 1:3:6 cement/coarse aggregate/fineaggregate mix.

Average to low compressive strength, but verystrong compared to w alls.

6.2 Builder The builder does not typically live in this building type. In most situations, the structure is built on the request of theowner and as per his requirements.

6.3 Construction Process, Problems and Phasing This construction is typically constructed by groups of skilled and semi-skilled masons and artisans. The foundationsare constructed from stone boulders (if locally available) or from bricks with lean cement mortar. The walls areconstructed from brick masonry and lean cement mortar. RCC roof slabs are often constructed by the same groupwithout any design specification for size and placement of reinforcement. In cities, simple tools such as hand-operatedconcrete mixers are used in some cases. In large portions of western and southern India, the climate is very hot andgood quality water is not easily available. In such situations, the cement mortar and concrete may not be adequatelycured. The construction of this type of housing takes place incrementally over time. Typically, the building is

originally not designed for its final constructed size. In urban areas, additional floors are often added withoutconsidering structural aspects. The construction is therefore staggered and a gap of several years may exist between theconstruction of different portions of the building. In rural areas where population density is lower, the buildings tendto expand horizontally and not vertically.

6.4 Design and Construction Expertise In rural areas, the masons may not have formal training. In urban areas, most masons have craftsman training. Theconstruction process in urban areas is controlled by the contractors whose commitment to quality may bequestionable. In rural areas engineers and architects do not play any role. In urban areas, the structural design may becarried out by the architect. Engineers and architects are typically not involved in construction. In many cases, thearchitectural and structural design is also carried out by the contractor since development control rules, where they exist,and very seldom enforced.

6.5 Building Codes and Standards This construction type is addressed by the codes/standards of the country. This type of construction is covered byseveral Indian Standards. IS 1905-1987 Code of practice for structural uses of unreinforced masonry (3rd edition) wasfirst published in 1961. IS 4326-1993 Earthquake resistant design and construction of buildings (2nd revision) wasfirst published in 1967 and has several sections pertaining to unreinforced brick construction. Earthquake resistance isalso addressed in IS 13828-1993 Improving earthquake resistance of low strength masonry buildings - Guidelines, andIS 13935-1993 Guidelines for repair and seismic strengthening of buildings. The year the first code/standard

addressing this type of construction issued was 1967. The most recent code/standard addressing this construction

type issued was 1993. Title of the code or standard: This type of construction is covered by several Indian Standards.IS 1905-1987 Code of practice for structural uses of unreinforced masonry (3rd edition) was first published in 1961. IS4326-1993 Earthquake resistant design and construction of buildings (2nd revision) was first published in 1967 andhas several sections pertaining to unreinforced brick construction. Earthquake resistance is also addressed in IS 13828-1993 Improving earthquake resistance of low strength masonry buildings - Guidelines, and IS 13935-1993 Guidelinesfor repair and seismic strengthening of buildings. Year the first code/standard addressing this type of constructionissued: 1967 When was the most recent code/standard addressing this construction type issued? 1993.

Building codes are rarely enforced. There is no formal procedure for enforcing the building codes.

6.6 Building Permits and Development Control Rules This type of construction is a non-engineered, and authorized as per development control rules.

Are building permits required? Yes, in large cities e.g. Mumbai; permits are not required in smaller municipalities andvillages. Building permits are not required to build this housing type.

6.7 Building Maintenance

Typically, the building of this housing type is maintained by Owner(s).

6.8 Construction Economics In urban areas, the cost of construction is in the range of Rs. 4,500 to Rs. 5,500 per m² (US$ 90-110 per m²). In ruralareas, the cost is by approximately 10-25 % lower due to lower labor cost and possibly due to inferior quality ofwork. Single family dwelling is typically constructed in about 3 months employing about 15 people. In multi-storybuildings, the time of construction may be much longer. Slabs are generally cast in a single operation and may requireabout 50 to 60 persons working for 12 to 18 hours.

7. Insurance

Earthquake insurance for this construction type is typically unavailable. For seismically strengthened existingbuildings or new buildings incorporating seismically resilient features, an insurance premium discount or morecomplete coverage is unavailable. Earthquake insurance for residential dwellings is not currently available in India.

8. Strengthening

8.1 Description of Seismic Strengthening Provisions

Strengthening of Existing Construction :Seismic Deficiency Description of Seismic Strengthening provisions used

Lack of integrity (box-type action) Installation of seismic belt (bandage) at the lintel level; it consists of w elded w ire mesh installed above the

lintel level and anchored to the w all. The mesh is covered w ith a thin cement plaster overlay (see Figure 7B) Cracks in the w alls In case of small cracks, pressure injection of epoxyh grout; in case of large cracks, filling the gaps w ith cement

grout and jacketing w ith reinforced cement overlay. (Source: IAEE 1986), see Figure 7H. Inadequate w all resistance (shear and

tensile) Reinforced concrete jacketing. Difficult to find skilled labor and materials for w elded w ire mesh in rural areas

Flexible floor/roof diaphragm

(Corrugated metal sheets/timber) Installation of RC roof band (bond beam). Provision of roof band is expected to enhance the overall intergrity

and improve torsional resistance of building Cracking/damage of w all corners (dueto improper interlocking of cross

w alls)

Corner strengthening of w all corners - installation of w elded w ire mesh anchored to the w alls w ith steel

dow els and covered w ith a thin cement plaster overlay (GOM 1998), see Figure 7C.

Strengthening of New Construction :SeismicDeficiency Description of Seismic Strengthening provisions used

Roof Reinforced concrete roof band; provision of roof band results in an improved overall integrity and torsional resistance of the building. Wall RCC lintel band; very effective, how ever skilled labour and materials may not be available, see Figures 7D, 7E and 7F Wall Improved quality of masonry (bricks and mortar) use of better quality bricks w ill drastically improve the w all seismic resistance; use or

richer cement/sand mortar w ill improve w all shear resistance. Wall Provision of vertical reinforcement at w all corners and intersections, see Figure 7G (Source: IAEE 1986)

A summary of key seismic strengthening provisions for this construction type is presented in Figure 7a.

8.2 Seismic Strengthening Adopted

Has seismic strengthening described in the above table been performed in design and construction practice, and if so,to what extent? Yes. Seismic strengthening was implemented after the 1993 Maharashtra earthquake. Some existing buildings werestrengthened after the earthquake, however majority of new masonry buildings were constructed with seismicprovisions incorporated.

Was the work done as a mitigation effort on an undamaged building, or as repair following an earthquake? Repair and strengthening following earthquake damage.

8.3 Construction and Performance of Seismic Strengthening

Was the construction inspected in the same manner as the new construction? Yes. It was a major government-sponsored program.

Who performed the construction seismic retrofit measures: a contractor, or owner/user? Was an architect or engineerinvolved? The construction was performed by the contractors, and the owners were overseeing the construction.

What was the performance of retrofitted buildings of this type in subsequent earthquakes? Retrofitted buildings were not subjected to the damaging earthquake effects as yet.

Figure 7A: Seismic Strengthening Techniques - ASummary

Figure 7B: Seismic Strengthening Techniques -Lintel Bandage

Figure 7C: Seismic Strengthening Techniques -Corner Strengthening

Figure 7D: An Example of New Constructionw ith Sesimic Features (note RC lintel band)

Figure 7E: Construction of RC Lintel Band

Figure 7F: Construction of RC Lintel Band -Pouring of Concrete Completed

Figure 7G: Seismic Strengthening of NewConstruction - Provision of Vertical Reinforcementat Wall Corners and Intersections (Source: IAEE

1986)Figure 7H: Repair of Wall Cracks by Epoxy

Injection (Source: IAEE 1986)

Reference(s)1. Innovative Earthquake Rehabilitation in India

EERILessons Learnt Over Time, Vol.2, Earthquake Engineering Research Institute, Oakland, USA

2. Manual for Earthquake-Resistant Construction and Seismic Strengthening of Non-Engineered Buildings inRural Areas of MaharashtraGOMRevenue and Forests Department, Government of Maharashtra, Mumbai, India 1998

3. Damage Survey Reports of Koyna, Killari and Jabalpur Earthquakes in published literature

4. Guidelines for Earthquake-Resistant Non-Engineered ConstructionIAEE

The International Association for Earthquake Engineeing, Tokyo, Japan (also available via Internet at w w w .nicee.org) 1986

5. The Bhuj Earthquake of January 26, 2001 - Consequences and Future ChallengesDepartment of Civil Engineering, Indian Institute of Technology Bombay, India and Earthquake Disaster Mitigation Research Center (EdM),Miki, Hyogo, Japan (CD-Rom) 2001

Author(s)1. Ravi Sinha

Professor, Civil Engineering Department, Indian Institute of Technology BombayCivil Engineering Department, Indian Institute of Technology Bombay, Mumbai 400 076, INDIAEmail:rsinha@civil.iitb.ac.in FAX: (91-22) 2572-3480, 2576-7302

2. Svetlana N. BrzevInstructor, Civil and Structural Engineering Technology, British Columbia Institute of Technology3700 Willingdon Avenue, Burnaby BC V5G 3H2, CANADAEmail:sbrzev@bcit.ca FAX: (604) 432-8973

Reviewer(s)1. Svetlana N. Brzev

InstructorCivil and Structural Engineering Technology, British Columbia Institute of TechnologyBurnaby BC V5G 3H2, CANADAEmail:sbrzev@bcit.ca FAX: (604) 432-8973

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